Datasheet

 2010-2017 Microchip Technology Inc. DS30009977G-page 297
PIC18F66K80 FAMILY
21.4.3.4 7-Bit Address Masking Mode
Unlike 5-bit masking, 7-Bit Address Masking mode
uses a mask of up to 8 bits (in 10-bit addressing) to
define a range of addresses that can be Acknowl-
edged, using the lowest bits of the incoming address.
This allows the module to Acknowledge up to
127 different addresses with 7-bit addressing, or
255 with 10-bit addressing (see Example 21-3). This
mode is the default configuration of the module, which
is selected when MSSPMSK is unprogrammed (‘
1’).
The address mask for 7-Bit Address Masking mode is
stored in the SSPMSK register, instead of the SSP-
CON2 register. SSPMSK is a separate hardware regis-
ter within the module, but it is not directly addressable.
Instead, it shares an address in the SFR space with the
SSPADD register. To access the SSPMSK register, it is
necessary to select MSSP mode, ‘
1001’ (SSP-
CON1<3:0> =
1001) and then read or write to the loca-
tion of SSPADD.
To use 7-Bit Address Masking mode, it is necessary to
initialize SSPMSK with a value before selecting the I
2
C
Slave Addressing mode. Thus, the required sequence
of events is:
1. Select SSPMSK Access mode (SSP-
CON2<3:0> =
1001).
2. Write the mask value to the appropriate
SSPADD register address (FC8h).
3. Set the appropriate I
2
C Slave mode (SSP-
CON2<3:0> =
0111 for 10-bit addressing, 0110
for 7-bit addressing).
Setting or clearing mask bits in SSPMSK behaves in
the opposite manner of the ADMSKx bits in 5-Bit
Address Masking mode. That is, clearing a bit in
SSPMSK causes the corresponding address bit to be
masked; setting the bit requires a match in that
position. SSPMSK resets to all ‘
1’s upon any Reset
condition and, therefore, has no effect on the standard
MSSP operation until written with a mask value.
With 7-bit addressing, SSPMSK<7:1> bits mask the
corresponding address bits in the SSPADD register.
For any SSPMSK bits that are active (SSPMSK<n> =
0),
the corresponding SSPADD address bit is ignored
(SSPADD<n> =
x). For the module to issue an address
Acknowledge, it is sufficient to match only on
addresses that do not have an active address mask.
With 10-bit addressing, SSPMSK<7:0> bits mask the
corresponding address bits in the SSPADD register.
For any SSPMSK bits that are active (=
0), the
corresponding SSPADD address bit is ignored
(SSPADD<n> =
x).
EXAMPLE 21-3: ADDRESS MASKING EXAMPLES IN 7-BIT MASKING MODE
Note: The two Most Significant bits of the
address are not affected by address
masking.
7-Bit Addressing:
SSPADD<7:1> = 1010 000
SSPMSK<7:1> = 1111 001
Addresses Acknowledged = ACh, A8h, A4h, A0h
10-Bit Addressing:
SSPADD<7:0> = 1010 0000 (The two MSb are ignored in this example since they are not affected)
SSPMSK<5:1> =
1111 0011
Addresses Acknowledged = ACh, A8h, A4h, A0h